In our daily lives, the electronic devices for adjusting voltage signals, such as the variable resistors, can be seen everywhere. According to the type of operation, the variable resistors can be sorted as rotating-type variable resistors and slide-type variable resistors.
FIG. 1 is an explosive view of a conventional slide-type variable resistor. As shown, the variable resistor PA100 includes a circuit base PA1, a manipulating module PA2 and a shell PA3. The circuit base PA1 includes a circuit board PA11 and a plurality of connecting ends PA12. The manipulating module PA2 includes a brush base PA21, two metal brushes PA22, a sliding bar PA23, an elastic unit PA24, and a washer PA25. The brush base PA21 is movably positioned on the circuit board PA11 along the operation direction L. The two metal brushes PA22 are located on a rear surface of the brush base PA21 for pressing against the resistance circuit on the circuit board PA11. The sliding bar PA23 is located on a front surface of the brush base PA21 and passes through the elastic unit PA24 and the washer PA25 in a serial. The shell PA3 is fixed on the circuit base PA1. The shell PA3 also has a position restriction hole PA31 and a plurality of fixing parts PA32. The sliding bar PA23 extends outward from the position restriction hole PA31. The fixing parts PA32 are utilized to have the shell PA3 fixed on the circuit base PA1.
Please also refer to FIG. 2, which is a cross-section view of the conventional slide-type variable resistor. As shown, because the metal brush PA22 is functioned to press against the resistance circuit PA111 of the circuit board PA11, after using for a while, the generated carbon particles would be accumulated on the two sides of the resistance circuit PA111 by the rubbing movement of the metal brush PA22 on the resistance circuit PA111. In addition, because the resistance circuit PA111 is usually positioned close to the conductive circuit, the accumulated carbon particles may cause short circuit between the resistance circuit PA111 and the conductive circuit and further damage the variable resistor PA100. In addition, the accumulated carbon particles may cause the generation of abnormal output signals as the metal brushes is moving.
In addition, because the position restriction hole PA31 is linked to the environment, there might be foreign matters falling into the position restriction hole PA31 to influence the sliding movement of the brush base PA21 or liquid flowing into the position restriction hole PA31 to cause pollution on the circuit board PA11 and electric failure. For example, the debris dropped on the circuit board PA11 when eating food might be stuck on the brush PA22 to influence the sliding operation during the movement of the brush base PA21, or the liquid poured out on the circuit board PA11 when the drink is knocked over might cause circuit failure. In addition, after the variable resistor being used for a while, environment particles might be accumulated on the circuit board PA11 to cause electronic failure.